Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 180538 AAB

Area Forecast Discussion...UPDATED
National Weather Service BROWNSVILLE TX
1138 PM CST Tue Jan 17 2017

.DISCUSSION...Updated for latest aviation discussion below.

.AVIATION...MVFR to prevail with a weak cold front slowly moving
west to east tonight into Wednesday. Occasional IFR cigs and MVFR
vsby within increasing showers and isolated thunderstorms. The
better opportunity for thunder will be Wednesday after 6 am and just
ahead of the front but probabilities and coverage are too low to
mention in the 06Z TAF package. The front to move east of KMFE
around Noon then slow down as it approaches the coast between 3 and
6 pm. A slow lifting of the MVFR cigs across western areas with
lower cigs and possible lower vsby persisting in some fog depending
on how far the front moves east.

.PREV DISCUSSION... /issued 557 PM CST Tue Jan 17 2017/
DISCUSSION...Updated for latest aviation discussion below.

MVFR ceilings will be the predominate condition this evening with
cigs lowering to IFR overnight and persisting into Wednesday
morning as low level moisture deepens in advance of stationary
front over South Texas. This front is expected to begin moving
southeast Wednesday morning moving slowly eastward. Showers and
some thunderstorms are expected to increase in coverage late
tonight and through the day Wednesday. Some patchy fog to develop
at times when rain becomes more persistent. South to southeast
winds become light tonight and remain light Wednesday.

PREV DISCUSSION... /issued 251 PM CST Tue Jan 17 2017/

SHORT TERM (Now through Wednesday Night): A somewhat active short
term period is expected with a quasi-stationary frontal boundary
draped across South Texas...but north of our area. Moisture pooling
into the region has kept isolated to scattered showers along the
coastal areas. Meanwhile...mid level moisture is being streamed over
the region as much of the region remains under a broad area of
ascent ahead of an approaching H5 low over the Desert Southwest.

Over the next 24 to 36 hours...the H5 low will slowly but steadily
move northeast in the Panhandle Regions and into the Central Plains.
As the system moves...the aforementioned frontal boundary will
progress eastward into the northwestern Ranchlands and Brush Country
later this evening and into Wednesday morning. The front will act as
a focus for showers and thunderstorms tonight over the western half
of the CWA. There is the potential for isolated severe storms late
this evening and overnight across the northwest...with hail being
the main concern. However...warm low to mid level temps will limit
that potential.

The front will push east towards the coast by Wednesday afternoon
with winds shifting to the west and northwest and rain generally
tapering off behind it. Moisture convergence from onshore/east flow
will kept some chances for showers and isolated thunderstorm over
the eastern portions of the CWA through part of the day.
However...there may actually be a lull in the precip during the

Another round of showers and some convective activity will be
possible again Wednesday night as the base of the H5 trough pivots
across central Texas. There will be better dynamics aloft with
somewhat stronger 850mb and 500mb winds from the southwest.
However...winds at the surface will be from the northwest still. As
such do not expect...widespread thunderstorm or any severe
weather...with storms remaining elevated in nature.

LONG TERM (Thursday through Tuesday): The forecast period begins
with a 500mb low/trough over the Texas panhandle with a frontal
boundary pushing off the Lower Texas coast. Rain chances will
quickly end from west to east on Thursday as the upper level
low/trough moves to the northeast and winds aloft become west to
northwest. This will result in much drier and more stable air across
the region late Thursday into Friday. The drier and more zonal 500
mb flow in addition to the increasing daytime heating will allow the
temperatures to warm steadily for Friday and Saturday with near
record to record breaking heat. However, a weak shortwave trough is
expected to move over Deep South Texas Friday supporting a slight
chance of showers across the eastern half of the CWA, mainly along
and east of IH-69C.

Another weak shortwave trough is expected to move across southwest
Texas Saturday before a strong 500mb low develops over the southern
plains Saturday night into Sunday. The next cold front will arrive
late Saturday night into Sunday morning. No rain is expected with
this front due to very limited moisture. Strong northwest winds will
develop in the wake of the front Sunday with very dry air. Wind
Advisories and Red Flag Warnings for wildfire potential are likely
across the Deep South Texas Sunday courtesy of the frontal

MARINE: (Now through Wednesday Night): Current Buoy 42020
observations show SE winds of 10 to 15 knots and seas around 5 feet.
Weak surface low pressure over the RGV will keep persistent S to SE
flow and some moderate swells across the offshore waters tonight
through Wednesday. The surface low will move north and east on
Wednesday...with a weak frontal passage shifting winds to the north
west by late Wednesday night...with broad surface high pressure
setting up over the Lower Texas Coast. Showers and thunderstorms
will be possible through the period.

Thursday through Sunday...Light northwest winds will prevail
across the coastal waters Thursday as a weak frontal boundary
moves offshore of the lower Texas coast. Winds will become
southeast on Friday as a warm front moves north Thursday night.
Winds should be light and variable across the western Gulf of
Mexico Saturday as the pressure gradient remains fairly weak.
Another cold front arrives late Saturday night into early Sunday
morning bring very strong northwest winds across the coastal
waters on Sunday. A Gale Warning will be possible Sunday afternoon
through Sunday night across the marine areas.



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